Methods and apparatus for passive thrust vectoring and plume deflection

ABSTRACT

A flow vectoring turbofan engine employs a fixed geometry fan sleeve and core cowl forming a nozzle incorporating an asymmetric convergent/divergent (con-di) and/or curvature section which varies angularly from a midplane for reduced pressure in a first operating condition to induce flow turning and axially symmetric equal pressure in a second operating condition for substantially axial flow.

BACKGROUND INFORMATION

1. Field

Embodiments of the disclosure relate generally to propulsion systemsand, more particularly, to methods and apparatus for passive thrustvectoring and plume deflection.

2. Background

Achieving in-flight thrust optimization with simultaneous minimizationof exhaust jet (or flap) interaction and low wing flap dynamic loadingon an aircraft with a close coupled engine installation is a significantdesign challenge.

SUMMARY

An example flow vectoring turbofan engine disclosed herein includes afixed geometry fan sleeve and core cowl forming a nozzle, the nozzleincorporating asymmetric convergence/divergence (con-di) and wallcurvature varying angularly from a midplane, a first degree of the wallcurvature being implemented during a first operating condition to reducepressure, and a second degree of the wall curvature being implementedduring a second operating condition to induce flow turning and axiallysymmetrically equal pressure.

An example jet propulsion device is disclosed herein. The example jetpropulsion device disclosed herein has a flow vectoring duct for abypass engine and includes a substantially annular exhaust ductsurrounding a jet engine center body forming a pair of concentricopposing inner and outer walls; a throat region asymmetricallypositioned in the outer wall of the exhaust duct forming a region ofconvergence, where the inner and outer walls converge, an amount ofconvergence varying longitudinally along the walls; and a region ofdivergence, where the inner and outer walls diverge, an amount ofdivergence varying longitudinally along the walls.

An example fixed geometry differential vectoring nozzle for a jetpropulsion device is disclosed herein. The example nozzle disclosedherein includes a first wall portion having a first curvature and afirst exit; a second wall portion having a second curvature and a secondexit varying longitudinally with respect to the first curvature toinduce lower pressure proximate the second wall portion relative topressure proximate the first wall portion in a first operating conditionand substantially equal pressure proximate the first and second wallportions in a second operating condition.

An example method for fan nozzle plume vectoring in a turbofan engine isdisclosed herein. The example method includes providing a fan nozzlehaving an asymmetric convergence and divergence (con-di) section withgreater con-di in a bottom portion of the fan nozzle relative to a topportion; operating the fan nozzle below a choke threshold to reducepressure in the bottom portion of the fan nozzle having greater con-difor differentially inducing circumferential flow resulting in the fannozzle flow being vectored toward the bottom portion; and operating thefan nozzle above the choke threshold for substantially uniform pressureacross the con-di section to produce substantially axial flow.

An example method for vectoring exhaust gas air flow passing through asubstantially annular exhaust bypass duct of a bypass jet engine isdisclosed herein. The example method includes positioning a jet enginehaving a bypass duct beneath a wing such that unvectored jet exhaustflow from the bypass duct in a choked condition is proximate a trailingedge flap of the wing; and contouring a predefined portion of a bypassduct distal to the trailing edge flap to redirect and vector a portionof the air flow in the bypass duct in an unchoked condition away fromthe trailing edge flap to reduce an interaction between the jet exhaustand the trailing edge flap.

An example method for vectoring flow in a fixed geometry nozzle isdisclosed herein. The example method includes configuring a nozzle withconvergence and divergence and an exit position providing anasymmetrical sectional area ratio from a first portion of the nozzle toa second portion of the nozzle; operating the nozzle in a chokedcondition with an exit flow from the nozzle being substantially axial;and operating the nozzle in an unchoked condition for differentialvectoring of the exit flow from the first portion of the nozzle towardthe second portion.

The features, functions, and advantages that have been discussed can beachieved independently in various embodiments of the present disclosureor may be combined in yet other embodiments further details of which canbe seen with reference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of a turbofan engine nacelle employing a firstembodiment;

FIG. 1B is a top view of a single side of the nacelle of FIG. 1A whichis symmetric about a midplane;

FIG. 1C is an isometric view of the nacelle of FIG. 1A;

FIG. 2 is a rear view of the nacelle of FIG. 1A;

FIG. 3A is a graph of normalized radius of the core cowl and fan sleeveat selected locations relative to a longitudinal reference station;

FIG. 3B is a graph of normalized sectional area of the fan nozzle atselected locations relative to a longitudinal reference station;

FIG. 4A is a graph of normalized pressure of the nozzle in an unchokedoperating condition measured at clock angles relative to the midplane;

FIG. 4B is a graph of normalized pressure measured at clock anglesrelative to the midplane for the nozzle operating in the chokedcondition;

FIG. 4C is a graph of thrust differential vectoring as a function ofnozzle pressure ratio;

FIGS. 5A-5C are graphs of radii of the core cowl/fan nozzle inner walland fan sleeve at upper, midline and bottom sections of a conventionalbaseline fan nozzle.

FIGS. 6A-6C are graphs of radii of the core cowl and fan sleeve atupper, midline and bottom sections of the fan nozzle for a firstembodiment;

FIGS. 7A-7C are graphs of radii of the core cowl and fan sleeve atupper, midline and bottom sections of the fan nozzle for a secondembodiment;

FIGS. 8A-8C are graphs of radii of the core cowl and fan sleeve atupper, midline and bottom sections of the fan nozzle for a thirdembodiment;

FIG. 9 is a graph of radii of the core cowl and fan sleeve demonstratingoperation at cruise with sonic flow at the nozzle throat;

FIGS. 10A, 10B and 10C are side, top and isometric views of a fourthembodiment in a turbofan nacelle;

FIG. 11 is a rear view of the nacelle of FIGS. 10A, 10B and 10C;

FIGS. 12A, 12B and 12C are side, top and isometric views of a fifthembodiment in a turbofan nacelle;

FIG. 13 is a rear view of the nacelle of FIGS. 12A, 12B and 12C;

FIG. 14 is a rear view of a round nozzle without centerbody for a jetengine;

FIGS. 15A, 15B and 15C are graphs of nozzle wall radii relative to anozzle axis for upper, midline and bottom sections of the round nozzleof FIG. 14;

FIG. 16 is a graph of the functional relationship between nozzlecurvature proximate the throat/exit and nozzle area ratio for thebaseline nozzle of FIGS. 5A, 5B and 5C embodiments described in FIGS.6A, 6B, 6C, 7A, 7B, 7C and 8A, 8B, 8C;

FIG. 17 is a flow chart of a method of flow vectoring employing theembodiments disclosed; and,

FIGS. 18A and 18B are exemplary flow visualizations for unchoked andchoked flow through one embodiment for vectoring away from a wing flap.

DETAILED DESCRIPTION

Traditional fixed geometry approaches to achieving in-flight thrustoptimization with simultaneous minimization of exhaust jet (or flap)interaction noise and low wing flap loading for fanjet engines haveinvolved compromise where neither individual objective was fullyachieved. An approach may be employed using variable geometry for thrustvectoring from the engine, but penalties may be incurred to propulsionsystem leakage and/or fuel burn, weight, complexity and/or failuremodes, and maintenance, all of which burden the aircraft. Additionally,a variable geometry solution is costly to manufacture relative to aconventional design. No existing cost effective solutions are availablefor the problem without design compromises. Known designs point thenozzle flow in a single direction that is neither ideal for high speedcruise performance nor ideal for low speed community noise or wing flapstructural weight. The result is non-optimum performance from both afuel flow and noise standpoint for the aircraft. Recent studies haveshown traditional design approaches can miss significant opportunitiesin reduced fuel burn and lower noise on close coupled engine and/orairframe installations.

It is therefore desirable to provide a fixed geometry thrustdifferential vectoring solution that simultaneously provides aircraftperformance optimization, low wing component loads, and minimization ofnoise. It is further desirable to provide a fixed geometry fan nozzle tocontrol exhaust plume direction differentially for high speed, highpressure ratio operation compared to low speed, low pressure ratiooperation.

Embodiments disclosed herein demonstrate modification of nozzle profilesfor jet propulsion devices including, for example, a turbofan orturbojet engine from a baseline symmetrical profile to a desiredasymmetrical profile with selected curvature and sectional area ratiowith clocked positioning. Such embodiments disclosed herein provide apressure differential to vector an exhaust plume in a desired directionwith unchoked flow through a nozzle while providing differentiallyvectored flow from the nozzle in a choked condition.

In some embodiments, turbofan engines with a fan sleeve and inner wallor core cowl as a centerbody create a fan nozzle with an asymmetricthree dimensional differential curvature and/or convergent/divergent(con-di) area ratio section in a region of the fan nozzle just upstreamof an exit. The geometry provided by embodiments disclosed hereinincludes two flow control regions. The nozzle geometry provided byembodiments disclosed herein results in a lower pressure portion near abottom of the nozzle exit relative to a top with the nozzle operating inan unchoked condition with subsonic or transonic fully expanded flowconditions such as, for example, take-off and approach. The flow at thetop of the nozzle is at relatively higher pressure traveling at a lowersubsonic Mach number. This pressure differential induces circumferentialmomentum causing the nozzle flow to be vectored downward away from thewing and/or flaps. Additionally, in some embodiments disclosed herein,specifically shaped exhaust nozzle chevrons may be integrated with thefan nozzle. The chevrons locally induce vortical mixing in the topportion of the flow to reduce a velocity gradient across the plume,locally redistributing energy away from the wing and/or flaps region.The vectoring and plume energy re-distribution provided by embodimentsdisclosed herein lower jet flap noise at take-off and approach. Atcruise, the operating nozzle pressure ratio is higher resulting in achoked flow at supersonic fully expanded flow conditions and the nozzlegeometry acts uniformly on the flow at a nozzle throat, which may belocated upstream of a nozzle exit. The uniformity of the pressureprovided by embodiments disclosed herein results in flow exiting thenozzle nearly (e.g., within a threshold) axially, thereby improvingand/or optimizing in-flight thrust. This flow direction difference, ordifferential vectoring, between lower and higher nozzle pressure ratiosprovided by embodiments disclosed herein enables the simultaneousimprovement and/or optimization of performance, reduced flap dynamicloading, and lower noise.

Alternative embodiments applicable for a round nozzle with no centerbody or a rectangular nozzle, such as those implemented in turbojetengines, demonstrate the differential vectoring effects created withasymmetric contour of the nozzle wall with resulting asymmetricsectional area ratio relative to the nozzle axis to achieve desiredpressure differentials between the unchoked and choked conditions.

Referring to the drawings, FIGS. 1A-1C and 2 show a first exemplaryembodiment of a turbofan engine nacelle 10 suspended from a mountingpylon 12. As in a conventional turbofan engine, a fan sleeve 14 and corecowl 16, acting as a center body, create concentric outer and innerwalls for an annular or substantially annular exhaust duct and flownozzle for a fan airstream. A standard core nozzle created by the corecowl 16 and an inner center body 18 directs jet flow from the enginecore. A reference plane 20 substantially normal to an axis of the nozzleis shown in FIG. 1A and is provided as a longitudinal measurementreference for relative shaping of the nozzle surfaces, as described ingreater detail below. The relative convergence and divergence of theinner and outer walls creates a minimum cross-sectional area with nozzlethroat profiles that vary longitudinally along the duct in anasymmetrical manner from the top through the bottom portion.

A top inner profile of the fan sleeve represented as line 22 shown inFIG. 1A taken in the plane represented by line 24 in FIG. 2 and a bottominner profile as represented by line 26 shown in FIG. 1A taken in theplane represented by line 28 in FIG. 2 is shown in FIG. 3A. In theexample of FIG. 3A, trace 30 represents the radius of the top innerprofile, represented by line 22 in FIG. 1A, and trace 32 represents theradius of the bottom inner profile, represented by line 26 in FIG. 1A.The profile radius (ordinate) for the concentric walls is shown relativeto longitudinal nacelle station (abscissa), in the engine with an originlocated at plane 20, which is described above. As shown in FIGS. 1 and3A, a lip or exit 34 of the bottom inner profile extends beyond an exit36 of the top inner profile creating a non-constant station outlet forthe embodiment shown. A non-constant station outlet may be non-constantstation, canted, non-planar, truncated or extended relative to thereference plane 20. The radius of the core cowl 16 forming the innerwall of the fan nozzle is shown as trace 37 in FIG. 3A.

The resulting local normalized cross-sectional flow area, A, divided byarea at the throat, A*, or A/A* of the fan nozzle is shown in FIG. 3Bwith the area along the top inner profile shown as trace 38 and the areaalong the bottom inner profile shown as trace 40. In such embodiments, aresulting nozzle throat 42 with respect to the bottom inner profile isproximal to the reference plane 20, while with respect to the top innerprofile the throat 42 is coincident with the exit 36, also proximal tothe reference plane 20. The asymmetric nature of the fan nozzle may bevisualized by, for example, comparing a convergent section 46 of thebottom inner profile area approaching the throat 42 and a divergentsection 48 between the throat 42 and the exit 34 of the bottom innerprofile and a converging upper section 44 terminating at the exit 36 ofthe top inner profile.

The asymmetry of the fan nozzle created by the varying profile from thetop inner profile to the bottom inner profile as defined above providesvectoring of the fan plume differentially depending on operatingcondition of, for example, a corresponding aircraft. The vectoringtransition occurs between nozzle pressure ratios of approximately 1.6 to1.9 for an exemplary embodiment. At pressure ratios less than a nozzlechoke threshold, the asymmetric diverging nozzle profile creates arelative low pressure region near a bottom portion 28 of the nozzlerelative to a top portion 24 (shown in FIG. 2). The flow at the topportion of the nozzle is at relatively higher pressure. This pressuredifferential results in the nozzle flow pointing downward away from thewing and/or flaps. At an approximate nozzle pressure ratio of greaterthan ((γ+1)/2)^(γ/(γ−1)), where γ is the specific heat ratio, a onedimensional sonic wave is created in the nozzle which results insubstantially equal pressure in the top and bottom portions of thenozzle providing axially symmetric flow. The dual flow control nature ofthe fan nozzle profiles in the top portion 24 and the bottom portion 28of the nozzle differentially act on the flow based upon the nozzleoperating subsonically (nozzle pressure ratio <1.89 for air as intake-off or approach) or supersonically (nozzle pressure ratio ≧1.89 forair as in higher altitude climb and cruise). The potential vectordifferential is on the order of 2 degrees.

Demonstrating the pressure differential with respect to a clocking angleθ about an engine centerline originating at a top of a midplane 54 (FIG.2) and in the vicinity of the reference plane 20 (FIG. 1), FIG. 4A showsa trace 56 for normalized pressure, P_(n) as a function of θ for anunchoked nozzle. Values in excess of one for P_(n) indicate a localstatic pressure greater than an average whereas values less than oneindicate local static pressure less than the average. For θ betweenabout −30° and −90° (nominally the top portion of the nozzle) pressureis significantly greater than from θ between about −90° and −180°. Thedifferential is particularly apparent when compared to normalizedpressure of a baseline symmetrical fan nozzle represented by trace 57.At nozzle pressure ratios greater than the threshold providing a chokedcondition in the nozzle, shown in FIG. 4B, normalized pressure remainssubstantially constant between the top portion and bottom portion of thenozzle as shown by trace 58 with a similar distribution profile to thatof a comparable conventional fan nozzle as shown by trace 59.

The difference in the pressure distributions of FIGS. 4A and 4B resultsin the differential thrust vectoring shown in FIG. 4C. A first vectoringregion 60 occurs when flow through the nozzle is unchoked. Pressuredifferential is created by the asymmetrical nozzle geometry and flowturning for vectoring of approximately 2° between the choked andunchoked operating conditions. Above a threshold pressure ratio (e.g.,1.6 for the illustrated example) a transition region 61 is entered inwhich the nozzle becomes partially choked, reducing the relativepressure differential and reducing vectoring. Above a second pressureratio (e.g., 1.89 for air) the nozzle is fully choked in region 262 andthe nozzle geometry acts uniformly on the flow at the nozzle throatwhich may be located upstream of the nozzle exit, as described in detailbelow. The uniformity of the pressure results in flow exiting the nozzleup to 2° different from the unchoked condition.

A conventional nozzle is symmetric around a nozzle axis. As a baselinerepresentation for inner and outer wall profiles, FIGS. 5A-5C representlongitudinal profiles of the baseline fan nozzle bounding walls for thefan sleeve (trace 62) and core cowl (trace 63) at θ sections ofapproximately (e.g., within a threshold) −30° (FIG. 5A), −90° (FIG. 5B)and −180° (FIG. 5C). The geometry in the baseline nozzle is independentof the θ angle. The nozzle may be convergent or convergent-divergent inarea ratio. The wall profiles are substantially (e.g., within athreshold) symmetrically constant resulting in sectional characteristicsof curvature and sectional area ratio being constant from top to bottom.The curvatures in the baseline nozzle are representative of a startinggeometry for modification with respect to curvatures and symmetry tocreate the differential vectoring of the embodiments disclosed herein.Actual dimensions and curvature of the nozzle will depend on the enginesize, application and numerous operating parameters which aresubstantially irrelevant to achieving the desired differentialvectoring. The specific nozzle shaping and asymmetric differential fromtop to bottom as well as longitudinal profile of the fan nozzle may betailored for specific engines, operating conditions and desiredvectoring performance.

FIGS. 6A-6C illustrate an example embodiment in which longitudinalprofiles of the radius are taken from the nozzle axis for the fan sleeveand core cowl at θ sections of approximately −30° (FIG. 6A), −90° (FIG.6B) and −180° (FIG. 6C). In the example of FIGS. 6A-6C, the inner wallprovides constant longitudinal profile (trace 64) with associatedrelative curvature comparable to the baseline as in FIGS. 5A-5C, and isnot a direct contributor to nozzle differential vectoring. In contrastto the baseline symmetric nozzle of FIGS. 5A-5C, the contour of theouter nozzle wall created by the fan sleeve in the example of FIGS.6A-6C varies from a first longitudinal profile 66 with associatedrelative curvature terminating at an exit 68 at θ≃−30° to an interimlongitudinal profile 70 with associated relative curvature terminatingat an exit 72 at θ≃−90° to a final longitudinal profile 74 withassociated relative curvature terminating at exit 76 at θ≃−180°. In theexample of FIGS. 6A-6C, the amount of con-di increases toward the bottomportion of the nozzle to create lower pressure than the top portion ofthe nozzle therefore inducing top-to-bottom flow within nozzle when itis unchoked. In the example of FIGS. 6A-6C, the length of the extensionto the exit (represented graphically in FIGS. 6A-6C as traces 68, 72,and 76) provides the over-area or con-di that vectors the flow. Thelength of the extension controls the amount of con-di in the nozzle. Thelonger the curve, the greater the A/A* of the nozzle. The example ofFIGS. 6A-6C relies primarily on the profile of the outer wall providedby the fan sleeve to generate lower pressure at the nozzle bottomrelative to nozzle top. When the nozzle is choked, the pressure at thenozzle throat becomes nearly uniform, as in FIG. 4B. This creates thedifferential vectoring between lower speed (e.g., take-off, unchoked)and higher speed (e.g., cruise, choked) operation.

FIGS. 7A-7C illustrate an example embodiment in which longitudinalprofiles of the radius for the fan sleeve and core cowl are taken at θsections of approximately −30° (FIG. 7A), −90° (FIG. 7B) and −180° (FIG.7C). Inner wall longitudinal profile 78 with associated curvatureprovided by the core cowl in the example of FIGS. 7A-7C is increasedbeyond that of the baseline nozzle in FIGS. 5A-5C and that of theexample of FIGS. 6A-6C to lower local pressure to allow the example ofFIGS. 7A-7C to be as effective as the example of FIGS. 6A-6C, but withless overall con-di. Although curvature in the profile 78 of FIGS. 7A-7Cis increased, it is still axi-symmetric as in the example of FIGS.6A-6C. The amount of con-di of the outer wall again increases towardsbottom portion of the nozzle, as shown, to create lower pressure thanthe top portion of the nozzle and, therefore, induces top-to-bottom flowwithin nozzle. Similar to the symmetric baseline geometry of FIGS.6A-6C, the contour of the outer wall created by the fan sleeve in theexample of FIGS. 7A-7C varies from a first longitudinal profile 80 withassociated relative curvature terminating at exit 82 at θ˜−30° to aninterim longitudinal profile 84 with associated curvature terminating atexit 86 at θ˜−90° to a final longitudinal profile 88 with associatedcurvature exit 90 at θ˜−180°. The example of FIGS. 7A-7C requires lesscon-di than the example of FIGS. 6A-6C due to local high curvature onthe inner wall through the throat. As with the example of FIGS. 6A-6C,the extension of the outer wall from the throat to the exit provides thedivergence in the nozzle to control the flow. However, the example ofFIGS. 7A-7C uses both con-di on the outer wall and relatively highercurvature of the inner wall. This induces the desired top-to-bottom flowwithin the nozzle at unchoked pressure ratios that becomes symmetricwhen the nozzle is operating choked to create the differential vectorbetween lower speed (e.g., take-off, unchoked) and higher speed (e.g.,cruise, choked). The example of FIGS. 7A-7C utilizes less con-di thanthe example of FIGS. 6A-6C, and relies instead on greater inner wallcurvature to be as effective as the example of FIGS. 6A-6C.

FIGS. 8A-8C illustrate an example embodiment in which longitudinalprofiles of the radius for the fan sleeve and core cowl are taken at θsections of approximately −30° (FIG. 8A), −90° (FIG. 8B) and −180° (FIG.8C). Unlike the constant curvature of the baseline inner wall of FIGS.5A-5C, the curvature of the inner wall (the core cowl) in the example ofFIGS. 8A-8C is greater at the bottom of the nozzle than the top with alongitudinal profile 94 and associated curvature at θ=−30°, longitudinalprofile 96 and associated curvature at θ=−90° and longitudinal profile98 with associated curvature at θ=−180°. In the example of FIGS. 8A-8C,the curvature of the inner wall varies from top (FIG. 8A) to bottom(FIG. 8C) by a factor of four. This reduces the need for con-diresulting from the outer wall shape relative to the example of FIGS.6A-6C or the example of FIGS. 7A-7C while maintaining effectiveness. Thecontour of the outer wall created by the fan sleeve the example of FIGS.8A-8C is a first longitudinal profile with associated relative curvatureterminating at exit 102 at θ=−30° to an interim longitudinal profile 104with associated relative curvature terminating at exit 106 at θ=−90° toa final longitudinal profile 108 with associated relative curvatureterminating at exit 110 at θ=−180°. This configuration also creates thedifferential vector between lower speed (e.g., take-off, unchoked) andhigher speed (e.g., cruise, choked) operation. The example of FIGS.8A-8C requires less con-di than the example of FIGS. 7A-7C, but requiresinstead greater inner wall curvature at the bottom relative to the topto be as effective as the example of FIGS. 7A-7C at differentialvectoring.

The asymmetry of the con-di and/or curvature from the upper portion ofthe nozzles to the lower portion of the nozzles as described for thethree above examples (the example of FIGS. 6A-6C, the example of FIGS.7A-7C, and the example of FIGS. 8A-8C) results in some degree of arearatio flare and nozzle wall curvature concentration located at or nearthe bottom portion of the nozzle. For the commercial turbofan nozzles asdescribed with respect to FIGS. 1A-C, 10A-C and 12A-C, this is farthestfrom the wing resulting in vectoring flow away from the wing in thesubsonic condition.

While described herein with the asymmetry referenced to a clock anglefrom a vertical midplane of the engine for desired downward vectoring ofthe jet plume to reduce interaction with an aircraft wing and flapsunder which the engine is mounted, vectoring using the embodimentsdisclosed herein may be accomplished in any desired direction between afirst portion of the nozzle and a second portion of the nozzle havinggreater area ratio and/or curvature to reduce pressure thereby vectoringthe flow by inducing flow from the first portion toward the secondportion below the threshold pressure ratio for an unchoked condition butproviding no vectoring above the threshold with the nozzle choked.

For each of the embodiments disclosed herein, once the nozzle isoperated choked (e.g., greater than the threshold pressure ratio),pressure in the region represented by line 112, shown in FIG. 9 in arepresentative section of the nozzle having an inner wall profile 114and an outer wall profile 116 transitions to a near constant value fromthe top of the nozzle to the bottom, as depicted in FIG. 4B. This nearconstant value pressure differential removes the inducement forvectoring of the flow. This difference in relative pressures created bythe choked or unchoked operating condition leads to a differentialvector between lower speed (e.g., take-off unchoked conditions) andhigher speed (e.g., cruise choked conditions) operation.

The actual nozzle exit configuration may vary depending on theoperational requirements of the engine. Example configurations for aturbofan engine common to commercial aircraft usage shown in FIGS.10A-10C and 11 include a nacelle 118 having a bottom chin 120 as opposedto a linear non-constant station shape of the exit. Tailoring of fansleeve and core cowl curvatures for this configuration (as previouslydescribed in connection with the examples of FIGS. 6A-6C, 7A-7C, and8A-8C) can be accomplished for the desired asymmetric pressuregeneration at unchoked flow conditions to provide differential vectoringof the flow. The example embodiment represented in FIGS. 10A-10C and 11is similar to the embodiment represented in FIGS. 1A-1C and 2, exceptthat the exit is no longer a single plane, with a linearly varying exitas a function of angular position but, rather, two separate offsetplanes. The two offset planes shown are perpendicular to the nozzle axisfor the embodiment of FIGS. 10A-10C and 11, and rather than smoothlyvarying the con-di from the top to the bottom, there is a narrow blendregion between the two planes, near the half-breadth (θ=−90°).Similarly, in some embodiments involving a nacelle 122 illustrated inFIGS. 12A-12C and 13, additional flow modification systems such aschevrons 124 a 124 b and 124 c, (and symmetric chevrons on the oppositeside of pylon 12) may extend from an upper portion of trailing edge 126of the fan sleeve. For the illustrated example of FIGS. 12A-12C and 13,six chevrons extend over approximately the top 25% of the circumferenceof the fan nozzle exit. The chevrons closest to the pylon 12, 124 a andthe symmetric chevron on the opposite side of the nacelle pylon extendfarther aft for enhanced mixing in the upper portion of the flow. Thechevrons of the illustrated example locally induce vortical mixing inthe top region of the flow to reduce a velocity gradient across theplume, locally redistributing energy away from the wing and/or flapsregion. The embodiment represented in FIGS. 12A-12C and 13 differs fromthat represented in FIGS. 10A-10C and 11 with the addition of chevronsto the portion of the nozzle proximate the wing and flaps. Chevrons maybe used to increase the pressure in the top portion of the nozzle in theregion of the reference plane 20 (FIG. 1). In some embodiments, a largernumber of chevrons may be employed or none at all.

Although the embodiments disclosed herein contain non-constant nacellestation nozzle exits, some embodiments may contain constant nacellestation nozzle exits with similar differential vectoring performance.

A round nozzle 128 or rectangular nozzle without a centerbody isillustrated in FIG. 14. The example of FIG. 14 may employ asymmetriccurvature between opposing walls in the nozzle for the differentialpressure generation in an unchoked condition. Contour relative to anozzle centerline axis 130, as shown in FIGS. 15A-15C, may be employedwhere longitudinal profiles of the radius for the nozzle wall relativeto nozzle centerline at θ sections of approximately 0° (FIG. 15A), −90°(FIG. 15B) and −180° (FIG. 15C). Contour of the outer nozzle wall variesfrom a first longitudinal profile 132 with associated relative curvature132 terminating at exit 134 at θ=0° to an interim longitudinal profile136 with associated relative curvature terminating at exit 138 at θ≃−90°to a final longitudinal profile 140 with associated curvatureterminating at exit 142 at θ≃−180°. The amount of con-di and/or wallcurvature increases toward the bottom portion of the nozzle to createlower pressure than the top portion of the nozzle, thereby inducingtop-to-bottom flow within the nozzle in the unchoked condition. Thisembodiment relies on the profile of the wall provided to generate lowerpressure at the nozzle bottom relative to nozzle top. When the nozzle ischoked, the flow becomes nearly uniform. This creates the differentialvector between lower speed (e.g., take-off, unchoked) and higher speed(e.g., cruise, choked) operation.

FIG. 16 demonstrates the varying effect of asymmetric variation ofcurvature and/or asymmetric sectional area ratio in the nozzle toachieve the desired pressure differential and, therefore, differentialvectoring. As a known definition of curvature, let N(s) be a regularparametric curve, where s is the arc length along the longitudinalstation. This determines the unit tangent vector T(s), and curvatureκ(s) is defined as the first derivative of T(s) and the secondderivative of N(s), κ(s)=T′(s)=N″(s). Local wall curvature (the secondderivative of position) and sectional area ratio for the baselineconfiguration described with respect to FIGS. 5A-5C is represented inFIG. 16 as circle 146. The baseline configuration represented by FIGS.5A-5C and shown as circle 146 in FIG. 16 can be represented as a singlecircle due to symmetry about the nozzle centerline, with its location onFIG. 16 notional. Circle 146 could be shown in other locations on FIG.16 and still adequately represent the baseline configuration shown inFIGS. 5A-5C. As represented by bar 148 for the example embodiment ofFIGS. 6A-6C, the sectional area ratio increases from a value of 1 thetop section represented by FIG. 6A through the 90° section representedby FIG. 6B to the 180° section represented by FIG. 6C where thesectional area ratio has increased to 1.02 providing asymmetry in thearea ratio from top to bottom of the nozzle. Because the local wallcurvature is constant for that embodiment, bar 148 is horizontal.Similarly, the example embodiment of FIGS. 7A-7C is represented by bar150. Again, the sectional area ratio increases from a value of 1 at thetop section represented by FIG. 7A through the 90° section representedby FIG. 7B to the 180° section represented by FIG. 7C where thesectional area ratio has increased to 1.015. However, the local wallcurvature is approximately 2 times the baseline curvature placing thebar upward on the graph. While the asymmetry of the sectional area ratiodoes not increase as much as for the example of FIGS. 6A-6C asrepresented by bar 148, the greater curvature results in comparableperformance. Finally, the example embodiment of FIGS. 8A-8C isrepresented by bar 152. Again, it is seen that the sectional area ratioincreases from a value of 1 at the top section represented by FIG. 8Athrough the 90° section represented by FIG. 8B to the 180 ° sectionrepresented by FIG. 8C where the sectional area ratio has increased to1.012. In this embodiment, the local wall curvature increases at greaterclock angle with approximately 2 times the baseline curvature at 90° and4 times the baseline curvature at 180° slanting the bar upward from leftto right on the graph. While the asymmetry in the sectional area ratiois not as large as for either the example of FIGS. 6A-6C or the exampleof FIGS. 7A-7C, asymmetry in the curvature accommodates the desiredpressure differential from top to bottom on the nozzle with a combinedperformance comparable to both the example of FIGS. 6A-6C and theexample of FIGS. 7A-7C for vectoring.

As shown in FIG. 17, an example method for flow vectoring employed bythe embodiments disclosed herein is accomplished by providing anasymmetric fan nozzle having greater area ratio and curvature in abottom portion of the nozzle relative to a top portion (block 1702). Thecon-di section can be created with a substantially axially symmetricinner nozzle wall with a constant curvature and a non-constant stationouter nozzle wall having an exit varying angularly about the midplanefrom minimum divergence at 20° from top midplane to a maximum divergenceapproaching bottom midplane (block 1703 a). Alternatively, curvature onthe inner nozzle wall may be increased while remaining symmetric andarea ratio of the lower sector of the outer wall relaxed proportionally(block 1703 b). Finally, the inner nozzle wall may not only incorporateincreased curvature but may be asymmetric with greater curvatureadjacent the desired lower pressure portion of the nozzle with furtherreduction of the area ratio (block 1703 c). Operating the nozzle below achoke threshold induces circumferential momentum resulting in the nozzleflow being vectored toward the most curved or highest area ratio portion(block 1704). Operating the nozzle above the choke threshold creates arelatively uniform pressure across the throat section of the nozzle toproduce substantially axial flow (block 1706). Chevrons may be providedadjacent the top portion of the fan nozzle to induce vortical mixing forreducing the velocity gradient across the plume (block 1708), tosupplement the vectoring.

For a conventional commercial aircraft, the method for controlling theexhaust gas air flow passing through an annular or nearly annularexhaust bypass duct of a bypass jet engine includes locating the jetengine beneath an airplane wing 160, as shown in FIG. 18A, such thatunvectored jet exhaust flow from a bypass duct 164 is proximate atrailing edge flap 162 of the wing. A predefined portion of a bypassduct is contoured, as disclosed for the example embodiments above, toredirect and vector a portion of the air flow in the bypass ductvectoring the exhaust plume 166 away from the trailing edge flap 162 toreduce the interaction between the jet exhaust and the trailing edgeflap. In some embodiments, the contoured portion of the bypass duct isdistal to the trailing edge flap. The operating condition shown in FIG.18A is the unchoked conditions resulting in downward vectoring of theflow while the operating condition in FIG. 18B is choked showingsubstantially axial flow of the plume 166′ in the cruise condition forthe wing.

As described in detail above, embodiments disclosed herein provide aflow vectoring turbofan engine having a fan sleeve outer wall and a faninner wall or core cowl forming a nozzle incorporating an asymmetricconvergent/divergent (con-di) section and/or curvature which varies froma convergent or nearly convergent area ratio and relatively relaxed wallcurvature at the top of the nozzle to a relatively greaterconvergent-divergent area ratio and more concentrated curvature at thebottom of the nozzle. This induces a top-to-bottom pressure gradientresulting in downward vectored flow when the nozzle is operatingunchoked (first operating condition) and axially symmetric equalpressure when the nozzle is choked (second operating condition) forsubstantially axial flow.

In some embodiments, the fan nozzle is for a turbofan engine mounted toan aircraft wing pylon and incorporates a non-constant nacelle stationoutlet terminating with a plurality of chevrons adjacent to the enginepylon. A differential convergent/divergent and curvature section variesangularly from a midplane and is located in a near exit region of thefan nozzle.

In some embodiments, a fixed geometry differential vectoring nozzle fora gas turbine engine employs a first wall portion having a firstcurvature and exit and a second wall portion having a curvature and exitvarying longitudinally with respect to the first curvature to inducelower pressure near the second wall portion relative to pressure nearthe first wall portion in a first operating condition and asubstantially equal pressure near the first and second wall portions ina second operating condition.

In operation, some embodiments provide a method for exhaust plumevectoring in a turbofan engine which is accomplished without movingparts by providing a nozzle having asymmetric con-di and curvaturethrough the throat and exit of the nozzle in relatively greater amountsalong the bottom portion of the nozzle relative to a top portion. Thenozzle is operated below a threshold for creating a sonic wave acrossthe entire throat (unchoked) to reduce pressure in the bottom portion ofthe nozzle having greater con-di and curvature for differentiallyinducing circumferential momentum resulting in the nozzle flow beingvectored toward that portion. The nozzle is operated above the thresholdfor creating a sonic wave across the entire throat (choked) resulting insubstantially uniform pressure across the throat section to producesubstantially axial flow.

Having now described various embodiments of the disclosure in detail asrequired by the patent statutes, those skilled in the art will recognizemodifications and substitutions to the specific embodiments disclosedherein. Such modifications are within the scope and intent of thepresent disclosure as defined in the following claims.

1. A flow vectoring turbofan engine, comprising: a fixed geometry fansleeve and core cowl forming a nozzle, the nozzle incorporatingasymmetric convergence/divergence (con-di) and wall curvature varyingangularly from a midplane for maximum con-di in a selected portion forreduced pressure in a first operating condition to induce flow turningand axially symmetrically equal pressure in a second operatingcondition.
 2. The flow vectoring turbofan engine as defined in claim 1,wherein the first operating condition comprises a nozzle pressure ratiobelow a threshold allowing unchoked flow through a throat and an exit ofthe nozzle.
 3. The flow vectoring turbofan engine as defined in claim 2,wherein the second operating condition comprises a nozzle pressure ratioabove the threshold creating a sonic wave for choked flow through thethroat of the nozzle.
 4. The flow vectoring turbofan engine as definedin claim 1, wherein the midplane is vertical and a selected portionhaving maximum con-di is a bottom portion of the nozzle for downwardvectoring of flow in the first operating condition.
 5. The flowvectoring turbofan engine as defined in claim 4, wherein the core cowlhas a symmetrical curvature and the fan sleeve exit is not aligned witha constant nacelle station having an exit.
 6. The flow vectoringturbofan engine as defined in claim 4, wherein the core cowl has asymmetrical increased curvature and the fan sleeve has decreasedasymmetrical con-di in the sleeve.
 7. The flow vectoring turbofan engineas defined in claim 4, wherein the core cowl has an asymmetricincreasing curvature, with a maximum curvature of the core cowl in thelower portion of the nozzle.
 8. The flow vectoring turbofan engine asdefined in claim 1, further comprising chevrons on an exit circumferenceof the nozzle.
 9. The flow vectoring turbofan engine as defined in claim8, wherein the chevrons span a top portion of about 25%-50% of thenozzle exit circumference.
 10. A jet propulsion device having a flowvectoring duct, the jet propulsion device comprising: a substantiallyannular exhaust duct surrounding a jet engine center body forming a pairof concentric opposing inner and outer walls; a throat regionsubstantially symmetrically positioned in the outer wall of the exhaustduct forming a region of convergence, where the inner and outer wallsconverge, an amount of convergence varying longitudinally along thewalls; and a region of divergence, where the inner and outer wallsdiverge, an amount of divergence varying longitudinally along the walls.11. The jet propulsion device as defined in claim 10, wherein theexhaust duct includes an outlet region; and the throat region is locatedin the near outlet region of the exhaust duct.
 12. The jet propulsiondevice as defined in of claim 11, wherein the throat region comprises asection of wall surfaces of the exhaust duct transitioning in anon-uniform manner, the section being located in the outlet region ofthe exhaust duct.
 13. The jet propulsion device as defined in claim 10,wherein an exit vector of an outlet plume at a first bypass engineoperating condition is different than the exit vector at a second bypassengine operating condition.
 14. The jet propulsion device as defined inclaim 13, wherein a difference between a planar angle of the exit vectorat the first operating condition and the second operating condition isin a range of between 0 to 5 degrees.
 15. The jet propulsion device asdefined in claim 10, further comprising an outlet not aligned with aconstant nacelle station.
 16. The jet propulsion device as defined inclaim 10, further comprising an outlet having chevrons.
 17. The jetpropulsion device as defined in claim 13, wherein the exit vector of theoutlet plume transitions at a nozzle pressure ratio of approximatelybetween 1.6 and 1.89.
 18. The jet propulsion device as defined in claim13, wherein a first transition from the first operating condition to thesecond operating condition at which differential directing of the plumecorresponds to a second transition between unchoked and choked operationof the nozzle.
 19. The jet propulsion device as defined in claim 13,wherein a first transition from the first operating condition to thesecond operating condition at which the differential directing of theplume occurs corresponds to a transition between a low speed operationand a high speed operation.
 20. The jet propulsion device as defined inclaim 19, wherein the low speed operation comprises at least one oftake-off or approach.
 21. The jet propulsion device as defined in claim19, wherein the high speed operation comprises at least one of cruise orclimb.
 22. A fixed geometry differential vectoring nozzle for a jetpropulsion device, the nozzle comprising: a first wall portion having afirst curvature and a first exit; and a second wall portion having asecond curvature and a second exit varying longitudinally with respectto the first curvature to induce lower pressure proximate the secondwall portion relative to pressure proximate the first wall portion in afirst operating condition and substantially equal pressure proximate thefirst and second wall portions in a second operating condition.
 23. Thenozzle as defined in claim 22, wherein the second curvature of thesecond wall portion is increased relative to the first wall portion. 24.The nozzle as defined in claim 22, wherein the second exit of the secondwall portion is extended longitudinally beyond the first exit of thefirst wall portion.
 25. The nozzle as defined in claim 22, wherein thefirst operating condition is unchoked flow and the second operatingcondition is choked flow.
 26. The nozzle as defined in claim 22, whereina second sectional area ratio associated with the second wall portion isgreater than a first sectional area ratio associated with the first wallportion. 27-33. (canceled)